Kinesiology 132 Systems Physiology II PDF

Kinesiology 132 Systems Physiology II Respiratory System – RS1 Today’s topics: Respiratory System – overview Ventilation General principles Boyle’s Law Pressures Inspiration and expiration Respiratory (RS) System – overview Focus of course:...

Kinesiology 132 Systems Physiology II Respiratory System – RS1 Today’s topics: Respiratory System – overview Ventilation General principles Boyle’s Law Pressures Inspiration and expiration Respiratory (RS) System – overview Focus of course: Ventilation: Air exchange between atmosphere and alveoli. Gas exchange: External respiration: gas exchange between alveoli and pulmonary capillaries. Internal respiration: gas exchange between tissue capillaries and interstitial fluid/tissue cells. Gas transport: Gas movement by pulmonary and systemic circulations between gas exchange locations. Ventilation – general principles At sea level atmospheric pressure varies; typically ~760 mmHg. Often report pressure changes as a relative change from atmospheric: 756 758 760 762 764 mmHg mmHg mmHg mmHg mmHg -4 -2 0 +2 +4 Ventilation driven by air pressure gradient: high to low pressure Breath in – inspiration: atmosphere (high pressure) to alveoli (low pressure). Breath out – expiration: alveoli (high pressure) to atmosphere (low pressure). Between breaths – pressures equalize between alveoli and atmosphere; no pressure gradient so no air movement for a moment. To get pressure gradient for ventilation: Need to manipulate pressure at alveolar level to get pressure gradients no matter what atmospheric pressure is doing. Ventilation – Boyle’s Law In a closed system at constant temperature, pressure (P) and volume (V) are inversely related (). Increase volume – decrease pressure. Decrease volume – increase pressure. Change volume – change pressure – create pressure gradient – produce ventilation. Boyle’s Law in action – interesting – but not testable Diving underwater into a hyperbaric (increased pressure) environment. Boyle’s Law at play in both directions: Descending: Pressure is increasing – volume decreasing. “Equalize” pressure – avoid pressure compression limits of some tissues. Ascending: Pressure is decreasing – volume is increasing. Expiration – avoid expansion limits of some tissues. Ventilation – 3 pressures Atmospheric Pressure (): Also known as air pressure or barometric pressure. Surrounding environment. Alveolar Pressure (): Within alveoli. Intrapleural Pressure ( Within intrapleural space between visceral and parietal pleura. Ventilation – intrapleural pressure Variable but always subatmospheric (lower than ). Creates a pressure gradient: Between alveolar and intrapleural: outward pressure – opposes lung elastic recoil (without this pressure gradient – lung collapses). Between atmospheric and intrapleural: inward pressure – opposes chest wall elastic recoil (without this pressure gradient – chest wall springs out). Pressures working together link lung and chest wall together so move as a unit. Atmospheric () / Alveolar () / Intrapleural (.  Ventilation – inspiration Diaphragm/external intercostals contraction Eupnea: 75% Diaphragm Contraction – downward flattening Thoracic cavity volume (~ 2cm). increases 25% External intercostals Contraction – Lung volume increases outward and upward movement of chest wall. becomes subatmospheric Air flows into lungs Eupnea: quiet, resting, unlaboured Ventilation – inspiration More forceful breathing: Diaphragm Contraction – stronger; more downward flattening (up to 10 cm). External intercostals Contraction – stronger; more outward and upward movement of chest wall. Accessory muscles of inspiration recruited (scalenes, sternocleidomastoid, pectoralis minor). Contraction – more outward and upward movement of chest wall. Result Greater increase in lung volume. decreases below atmospheric to greater extent (larger pressure gradient). Even more air flows into lungs.  Ventilation – expiration Diaphragm/external intercostals stop Eupnea: contraction Recoil to pre- inspiration positions. Recoil – thoracic cavity volume decreases Diaphragm Contraction ends – recoil back to dome shape. Lung volume decreases returning to pre-inspiration size External intercostals (compresses alveoli) Contraction ends – inward and downward recoil of becomes greater than chest wall. Air flows out of lungs Eupnea: quiet, resting, unlaboured Ventilation – expiration More forceful breathing: Diaphragm Contraction ends – recoil back to dome shape. External intercostals Contraction ends – inward and downward recoil of chest wall. Accessory muscles of expiration recruited (internal intercostals, abdominals). Contraction – more inward and downward movement of chest wall. Result Greater decrease in lung volume; more compression of alveoli. increases beyond atmospheric to greater extent (larger pressure gradient). Even more air flows out of lungs.